The demand for fresh water for oilfield operations has skyrocketed as a result of the boom in hydraulic fracturing for shale plays. A typical hydraulic fracturing treatment may consume, on average, three to five million gallons of water (usually freshwater). This is particularly problematic offshore, where freshwater must be transported to the well site, whereas seawater is readily available, if it could be used to formulate a good fracturing fluid. For additional reasons it is often desirable to form and use a fracturing fluid having a high content of inorganic salt, whether on land or offshore. For example, salt curbs bacterial action. Salt provides weight (that is, density) to a treatment fluid. Salt (e.g., KCl) usually reduces damage to production sands containing swellable clay.
Not many polymers perform well in brine, however, and even fewer perform well in hard brine such as seawater, which include a high concentration of divalent metal ions such as magnesium and calcium.